The deposition of material upon a substrate by the use of an electric arc is well known. FIG. 1 depicts a typical deposition apparatus 10. The process takes place in a vacuum chamber 12 which encloses a substrate 14 which is to be and an electric arc electrode assembly 16, having an anode 18 and a cathode 20. Material 24 to be deposited is placed in a receptacle 26 formed in the cathode 20 of the electric arc electrode assembly 16. The substrate 14 to be coated is placed near the electric arc electrode assembly 16. A potential is applied between the anode 18 and the cathode of the electric arc electrode assembly 16 and current flows between them, once the arc is ignited. As current flows between the cathode 20 and the anode 18, the material 24 to be deposited is vaporized and ionized forming a plasma 30 which maintains current flow even as the anode 18 and the cathode 20 are physically separated. The ions of the plasma 30 interact with the surface of the substrate 14 to be coated and are deposited thereupon. It should be noted, in the case where the cathode 20 is constructed from the material 24 to deposited, the cathode 20 need not contain a receptacle 24 and instead the cathode 20 itself is consumed in the deposition process. This form of deposition, in which material is deposited from the cathode region, may be termed cathodic vacuum arc deposition.
Alternatively, the anode 18 of the electric arc electrode assembly 16 may be used as the source of the material to be deposited. In such a case, where the material is deposited from the anode region, the deposition is referred to as anodic vacuum arc deposition.
In anodic vacuum arc deposition, an electric arc 30, which forms between the anode 18 and the cathode 20, is initiated by physical contact between the anode 18 and cathode 20. Once the electric arc 30 forms or ignites, the anode 18 and the cathode 20 are separated and the arc is maintained by the material ionized during initiation.